U.S. 2010/0110551 A1 discloses a multifunctional optical film for enhancing light extraction from a self-emissive light source. The multifunctional optical film comprises a flexible substrate, a structured layer of extraction elements having a first index of refraction and a backfill layer comprising a material having a second index of refraction different from the first index of refraction. A substantial portion of the extraction elements is in optical communication with a light emitting region of the self-emissive light source when the optical film is located against the self-emissive light source. The backfill layer forms a planarizing layer over the extraction elements, wherein a difference between an index of refraction of the structured layer and an index of refraction of the backfill layer is greater than or equal to 0.3.
Although the multifunctional optical film enhances the light extraction from a self-emissive light source, the light extraction efficiency is still relatively low.